How to make a racing lawn mower (Updated!)

Step 11 Updates: New rear axle chain tensioner.

Here's another update, and this time its again for the rear chain tensioner. I had a lot of issues with the chain jumping off the sprocket for the rear axle. I tried a few things, namely the experiment I mentioned in the previous step involving two roller skate wheels, one on top of the chain, one underneath. That system didn't work.

So I came up with a new tensioner that involves using a chain sprocket idler which is spring loaded. The old tensioner idler was mounted to a bracket with a slot cut in the side to enable the idler wheel to be moved up and down. This is shown in step 4. So I used the same bracket but instead of having the idle sprocket be stationary, it "floats" up and down in the slot with the help of a sturdy spring that ensures that it keeps constant pressure on the chain. I accomplished this by using 2 large fender washers on each side of the mounting bolt going through the bracket, then having nylock stop nuts on either side, backed up just enough to allow the mounting bolt to move freely up and down. I welded a bolt to the frame above the idler sprocket so that the tension spring could be attached. The idler sprocket itself is mounted to a thick piece of 1/8" steel.

This has worked out great all season. The tensioner can not only move up and down, but also slightly forward and back thus not matter what the chain does, the tensioner keeps constant pressure on it. With both chains staying put, the mower is now pretty reliable.

The rebuilt engine has held up great this year. Its now broken in so the synthetic oil stays almost crystal clear for a good 2-3 races.

We also just redesigned our web site and you can check us out at www.pvmowerracing.com

Comments

[McClellan41]

i have the same thing but not spring loaded its stationary and it has worked out great so far!!